Hierarchical porous carbon with tunable apertures and nitrogen/oxygen heteroatoms for efficient adsorption and separation of VOCs

Abstract

Porous carbon materials are good adsorbent candidates for removing volatile organic compounds (VOCs) due to their reliability and cost-effectiveness. Especially, the pore size distribution (PSD) of porous carbon materials plays a critical role in VOCs adsorption and separation. In this study, we present benzimidazole-derived porous carbons (BICs) with controllable pore size and oxygen/nitrogen heteroatoms. The pore size is controlled by adjusting the reaction degree of inorganic salt (K2CO3) and nitrogen-containing groups in the system. The tunable pore size distribution makes BICs highly efficient for the adsorption and separation of VOCs. BIC-3-900 exhibits a dominant pore size distribution of 3.0–4.0 nm and an exceptionally high total pore volume of 2.42 cm3/g, leading to ultra-high adsorption capacities for benzene and methanol (22.19 and 52.65 mmol/g, respectively) at 293 K. In addition, BIC-1-700 dominated by the micropore size is more favorable for adsorbing low-concentration small molecule VOCs (with a dynamic adsorption capacity of 4.21 mmol/g for methanol at 3800 ppm). In terms of the adsorptive separation performance, BIC-1-900 has an efficient benzene/methanol selectivity (∼30.13) due to its PSD (1.2–2.0 nm) which was more favorable for capturing low-concentration benzene. Moreover, both experimental and simulation (GCMC and DFT) results demonstrate that the abundant N/O heteroatoms doping in BIC-1-700 results in charge heterogeneity and stronger electrostatic affinity for polar VOCs molecules. Herein, our findings suggest that BICs with controllable pore size and oxygen/nitrogen heteroatoms have significant potential in practical VOCs capture and separation.